In recent years, terrorists' means of violent terrorist activities in public places become increasingly diversified, and various dangerous liquids such as dangerous chemicals or the like also become one of the means of terrorist activities prejudicial to the public. Thereby, requirements for security inspection of liquid carried with persons are put forward on the basis of security inspection of luggage and parcels. As a result, there is a need for an effective method and device for security inspection, so as to meet the requirements.
Currently, there are four methods for inspecting liquid, which are a chemical method, an electromagnetic method, a neutron method and a ray method. These methods will be described in detail below.
The chemical method comprises odor recognition, ion scanning detection, and material analysis. The odor recognition often cannot be used for achieving inspection due to a sealed package of the liquids in practical applications. The ion scanning detection is famous for its high sensitivity. However, the ion scanning detection has the following disadvantages that it has a high false alarm rate and is often influenced by the background environment. The material analysis has features of high precise and high accuracy. However, the material analysis needs to take some time to analyze and process samples, which cannot meet the requirements for on-site rapid inspection. In addition, the material analysis may cause chemical pollution.
The electromagnetic method is an active measurement approach, and is used to distinguish liquids from each other according to different dielectric constants of the liquid relative to electromagnetic waves. However, the electromagnetic method per se is easy to be adversely influenced by metal packages, thick material packages, irregular special-shaped bottles or the like. Therefore, the electromagnetic method has obvious limitations in practical cases that the packing materials are complicated, and thus cannot be used for achieving material recognition.
A phenomenon of “neutron activation” may occur during the use of the neutron method. That is, radiation residuals may exist in the liquids after the liquids are inspected by using the neutron method. In addition, due to strong penetrability of neutrons, a more complicated radiation shield may be needed for neutrons, and devices may occupy a large area and be inconvenient to carry, and thus are not suitable for use in most public places.
The ray method comprises a two-dimensional ray scanning technology and a CT technology. In general, the two-dimensional ray scanning technology is primarily used for inspecting luggage articles and cannot be used for judging whether liquid is dangerous, and the CT technology has an advantage that it is not influenced by packing materials, and can be used for inspecting liquids. However, the CT technology has a relatively low inspection speed, and cannot be used for recognizing materials or the like.
In conclusion, the four methods described above have disadvantages in terms of rapid security inspection and material recognition of the liquid. Therefore, there is a need for a practical method to meet the requirements for rapid security inspection and material recognition of the liquid.